Today, most automobiles utilize a viscous-type fluid coupling device to drive the radiator-cooling fan. Traditional viscous-type fluid coupling devices include an input coupling member and an output coupling assembly. The output coupling assembly includes a die-cast housing member (body), and a die-cast cover member (enclosure), the members being secured together by a rollover of the outer periphery of the cover member.
The fluid coupling device is adapted to be driven by the engine, and in turn, drives the radiator-cooling fan. The fan may be attached to the housing member by any suitable means.
The input coupling assembly typically includes a central shaft on which a clutch, or clutch plate is mounted. The input coupling assembly is typically either coupled directly to the engine crankshaft or indirectly to the crankshaft via a belt and pulley system, wherein the pulley is coupled to a hub that is coupled to the input coupling assembly. The pulley may also be coupled to an externally threaded waterpump shaft. The assembly functions as a support for the inner race of a bearing set, which is seated on the inside diameter of the housing member. The rotation of the input coupling assembly thus causes rotation of the input coupling assembly and waterpump shaft (if utilized).
The housing member and the cover member cooperate to define a fluid chamber, which is separated into a fluid operating chamber and a fluid reservoir chamber by the clutch and a reservoir plate. The fluid reservoir chamber is thus defined by the cover member and reservoir plate, while the fluid operating chamber is defined by the clutch and housing member. The reservoir plate is operatively coupled with the innermost end of the actuator shaft and contains a fill port through which viscous fluid flows from the fluid reservoir chamber to the fluid operating chamber.
Disposed adjacent the radially outer periphery of the operating chamber, the cover member includes a pumping element, also referred to as a “wiper” element, operable to engage the relatively rotating fluid in the operating chamber, and generate a localized region of relatively higher fluid pressure. As a result, the pumping element continually pumps a small quantity of fluid from the operating chamber back into the reservoir chamber through a radial passage defined by the cover member, in a manner well known in the art.
As one of ordinary skill recognizes, the output, or torque, to the body and cover in these systems is thus a function of the rotational speed of the clutch and the amount of viscous fluid contained within the working chamber. Further, a bimetallic element, or a valve arm capable of electronic control, is positioned near the fill port of the reservoir plate and controls the amount of viscous fluid flowing from the reservoir chamber to the working chamber. This allows for precise control of the torque output of the fan drive to the coupled fan blades at any given engine speed.
One problem with traditional viscous-type fluid coupling devices used to drive fans is the complexity of the system. A clutch is contained within the body and cover is required to drive the output. The clutch, and any associated parts, are expensive to manufacture and build and may be a source for failure within an automobile. It is thus highly desirable to simplify the design of viscous type fan drives.